A continuous casting device normally provides an ingot mold comprising a crystallizer inside which the liquid metal is cast, and a series of containing and guide elements, such as rolls or other similar means, which accompany the at least partly solidified cast product, and during the step of progressive solidification, between the exit from the ingot mold and the first elements that make up the rolling line, for example shears, a heating furnace, a first roughing cage or a rolling train.
Normally, the segment at exit from the ingot mold is curved, so as to connect the vertical or sub-vertical direction along which the casting is carried out and the horizontal direction in which rolling is performed.
By cast product, here and hereafter in the description, we mean a slab, a bloom a billet of various sizes and section.
Examples of such containing and guide elements can be seen for example in U.S. Pat. No. 5,630,467, where there are segments of rolls that have a progressively increasing section as they are distanced from the exit of the ingot mold, and mobile toward and away from the cast product, and curved continuous segments that accompany the completely solidified product and dispose it on the horizontal plane so as to send it to the rolling passes.
The presence of mobile roll elements at exit from the crystallizer is necessary so as to perform the soft reduction procedure, or reduction in thickness with liquid core, where the cast product is reduced in thickness, exploiting the fact that its inner core is not yet completely solidified.
Document U.S. Pat. No. 6,892,794 B2 shows a casting device in which, at exit from the ingot mold, there are consecutive segments of rolls that accompany the cast product in the step of progressive solidification, and in which the elements that support the cast product modify their conformation as the progressive increase in thickness of the solidified part of the product varies.
Normally, these containing and guide elements cooperate with so-called secondary cooling systems, to distinguish it from the primary cooling that takes place inside the ingot mold. Such secondary cooling systems contribute to define the solidification profile of the cast product, allowing to regulate the position of the so-called “kissing point”, that is, the point where the two solidified semi-skins of the cast product meet, for example as a function of the type of material and the final result to be obtained.
In the field of continuous casting it is also known, however, that as the type of steel to be produced varies, it is necessary to consequently adjust the casting parameters, in particular the speed of extraction of the product.
It is for example known that certain steels, for example so-called commercial steels, are cast at relatively high speeds, up to 6-7 m/min, while for other steels, for example high carbon content steels, medium alloy steels and others, the speed must be reduced to values in the range of about 3-4 m/min.
When the casting speed passes from the higher value to the lower value, the metallurgical length is proportionally reduced, even by 6-10 meters, and therefore, after the so-called kissing point where the metallurgical cone is closed, the cast product has to travel a longer segment and also at a lower speed, with a relative greater temperature loss compared with higher casting speeds.
This temperature loss entails a high waste of energy and also limits rolling fitness in terms of compression percentage downstream of the continuous casting.
DE 102 36 368 shows containing segments with rolls that can be equipped with heat insulation panels, for example vertical, disposed around the transit path of the cast product.
The purpose of the present invention is therefore to solve this shortcoming, proposing a solution that allows to adjust the heat conditions of the cast product at exit from the ingot mold to the variations in the casting speeds deriving, for example but not only, from modifications in the type of steel that is being cast.
Another purpose of the invention is to obtain this adjustment with a relatively simple and efficient solution which does not entail any extension of the casting line and that does not require the use of additional elements that modify the trajectory and/or bulk of the casting machine.
The Applicant has devised, tested and embodied the present invention to overcome the shortcomings of the state of the art and to obtain these and other purposes and advantages.